Safety and arming mechanism



NOV- 1 1960 E. N. sHr-:ELEY

SAFETY AND ARMING MECHANISM Filed June 5, 1959 DOA l WL HFQ. 5.0.5 N. NY M m E .n wnv. E,

2,958,286 Patented Nov. '1, 1960 SAFETY AND 'ARMING NIECHANISM Eugene N. Sheeley, Washington, D.C., assgnor to the lUnited States of America as represented by the Secretary of the Army Filed June 5, 1959, Ser. No. 818,489

1 Claim. (Cl. 102-78) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to an arming system which can be incorporated in a missile.

In certain military applications it is required that an arming system provide arming only when the missile has travelled a predetermined constant distance through the air at some predetermined minimum average velocity. The prior art has not been successful in providing a missile arming system which will meet these requirements, and it is therefore the object of this invention to provide an arming system which will do so.

According to this invention, an acceleration-responsive weight element, which is caused to move proportional to the air distance travelled by the missile, is combined with a timing means which prevents the weight element from reaching a nal position where it would arm the missile, should the weight element fail to reach this nal position within a predetermined period of time. Since incremental movements of the weight element represent substantially proportional distances traveled by the missile, arming at a predetermined distance is assured. Also, since the timing means prevents arming unless the missile has reached this predetermined distance within some predetermined minimum time, this eectively prevents the missile from arming unless it has travelled at some predetermined minimum average velocity in reaching this predetermined distance.

The specific nature of the invention, as well as other objects, used and advantages thereof, will clearly appear from the following description and from the accompanying drawing, in which:

Fig. l is a side view of the arming system of this invention with the cover removed.

Fig. 2 is an end View of Fig. 1, taken through lines 2 2 of Fig. 1, with the cover in place.

Fig. 3 shows the position of the Weight element and a timing gear should the missile burn-out `during the arming period.

Fig. 4 shows the relative positions which the weight element and the timing gear assume if the missile is traveling at the proper velocity during the arming period.

-Referring now to Figs. l and 2, an embodiment of the arming system in accordance with the invention is shown as comprising a base and a cover 11 (Fig. 2) which iits tightly over base 10. Housed within base 10 is weight 12 eccentrically depending from arm 13 which is journaled on shaft 14 (Fig. 2). Ann 13 thus will rotate counterclockwise (as viewed in Fig. l) on shaft 14 in response to missile acceleration in the direction of the arrow.

Shaft 14 (Fig. 2) has two ends, 15 and 16, which are respectively held by bracket 18 and base 10 by any suitable means. Bracket 18 is fixed to base 10 by means of machine screws 19. Coil spring 20 is coaxially wrapped around shaft 14 and has two ends, 21 and 22, which are aixed to bracket 18 and to the arm 13, respectively. Spring 20 resiliently urges arm 13 clockwise as viewed in Fig. 1. Shoulder 39 formed by a curvature in arm 13 is urged in engagement with cylinder 35 by spring 20. Cylinder 35 is fixed to weight 30 which is movable along rods 29 passing through bores 41 in the weight 30 in response to acceleration in the direction of the arrow (Fig. 1). Weight 30 is locked against downward movement from its initial or unarmed position (as shown in Fig. 2) by shoulder 39 engaging cylinder 35.

Weight 30 is a conventional form of acceleration-responsive weight element which is modified by forming a rectangular slot 31 in edges 32 and 33. Weight 30 is adapted to carry a detonator 38 downwardly from the unarmed position shown in Fig. 1 when cylinder 35 is released by rotation of shoulder 39 and arm 13 in response to missile acceleration. When weight 30 travels through distance E (Fig. 4), edge 33 will abut surface 34 on arm 13 because arm 13 will have rotated counterclockwise (Fig. 4) as a result of missile acceleration acting upon eccentric weight 12. When edge 33 abuts surface 34, detonator 38 will align with an explosive train 42 (Fig. 2) leading to the missile warhead in a conventional manner, thereby arming the missile.

Another edge of weight 30 is provided with a rack 36 which is engaged by conventional utterbar or starwheel escapement mechanism 37 which substantially performs the function of a double integrator so that weight 30 moves through incremental distances proportional to the distances traveled by the missile, and at a velocity proportional to the velocity of the missile.

Now if a tab 27 is suitably positioned as shown in Fig. l and provided with a suitable angular velocity, after some predetermined time, tab 27 will either engage edge 33 or slot 31 so as to lock the weight 30 from further movement (Fig. 3), or fail to contact edge 33 or slot 31 (Fig. 4) and contact smooth edge 32 so as to permit the weight 30 to travel the distance E and arm the missile (Fig. 4). It should be evident to those skilled in the art that since the weight 30 moves proportionally to the velocity of the missile, the above described arrangement assures that arming will occur only if the missile has travelled at a predetermined average Velocity in reaching the predetermined distance. Thus the missile must travel at some predetermined minimum velocity during the arming period and for some predetermined minimum distance or weight 30 will be locked against downward movement to the armed position by tab 27.

Timing gear 26 (Fig. 2) on which tab 27 is located is driven by means of coil spring 23. Coil spring 23 has ends 24 and 25 which are afxed to arm 13 and to gear 26, respectively. Spring 23 is under no initial tension and winds only when arm 13 rotates counterclockwise (Fig. 1). Flutterbar escapement mechanism 28 is provided to restrain spring-biased rotation of gear 26 so that tab 27 moves at essentially constant Ivelocity and can either engage or fail to engage edge 33 or slot 31.

The operation of the above-described arming system of this invention can be summarized as follows. The base ltl is properly positioned in the missile so that missile acceleration acting n the direction shown by the arrow in Fig. l causes counterclockwise rotation of eccentric weight 12. Rotation of weight 12 causes rotation of arm 13 which winds spring 23. Spring 23 upon winding, resiliently urges timing gear 26 to rotate counterclockwise as viewed in Fig. 1. Also, rotation of larm 13 causes shoulder 39 to disengage from cylinder 35 which is xed to weight 30. Weight 30 is thereby released for downward movement along rods 29 in response to forces of setback acting opposite in direction to that of the arrow in Fig. l.

Flutterbar escapement mechanism 37 can be designed of the accelerative forces acting on weight 30. On the other hand, tab 27 is being driven independently by spring 23 at aconstant angular rate. Thel distance travelled by tab 2"/ istherefore substantiallyv independent of alll other forces developed during missile launching; The action of tab 27 can be regarded as that of a clock, or timer which times the downward travel of weight 30-and thus the travel of the missile from launching. Since the travel of weight 30 is bein-g compared to the time it takes to tra'vel an incremental distance, the rotative movement of tab 27 acting againstl the linear travel of weight 30 determines whether or not the average velocity of weight 35j, and of the missile, is of some predetermined minimum value.

If the average velocity of the missile is below a predetermined minimum value, the downward distance travelled by weight 30 will not be suicient to prevent tabv 27 from rotating to a position under weight 30 to engage edge 33 or slot 31 and lock the weight 30 from further movement, thereby preventing arming as shown in Fig. 3. When the missile is ying at a proper average velocity, however, weight 30 will travel a suicient velocity to prevent tab Z7 from engaging either edge 33 or slot 31 with the result that tab 27 will only contact edge 32. Edge 32 is smooth so that weight 30 can continue its downward mo'vement even though tab 27 is riding against this edge. Weight 30 is thereby free to travel the distance E which will cause arming of the missile.

It will be evident from the foregoing that the present invention achieves the requirementof providing arming only when the missile has travelled a constant predetermined distance at some predetermined minimum average velocity. It is to be understood that for a given missile the movement of the weight 30 in relation to the angular velocity of the tab 27 may be chosen to provide any desired predetermined distance and predetermined minimum average velocity for which arming will be permitted to occur.

It is also to be understood that the embodiment shown is `only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claim.

I claim as my invention:

An arming system for use in a missile adapted to arm said missile only when said missile has traveled a predetermined constant distance at some predetermined average velocity, said, system comprising: a base, a shaft xed to Saidbase at one end thereof, an arm mounted for rotation on said shaft, an eccentric weight fixed to one end of said arm for causing rotation thereof in response to forces of acceleration produced by missile launching, a gear mounted for rotation on said shaft, an escapernent mechanism engaging said gear and limiting rotation thereof to a predetermined angular velocity, spring means connecting said gear to said arm and adapted to wind and thereby rotate said gear when said arm rotates in response to acceleration, a weight element movable towards said shaft from an initial to a final position in response to missile acceleration, a detonator housed in said weight element and movable therewith, an explosive train communicating with said detonator when said weight element reaches said final position, a rack on one edge of said weight element, a ilutterbar escapement mechanism engaging said rack and adapted to oscillate and thereby inhibit travel of said weight element to said nal position, said flutterbar escapement mechanism being so constructed that the accelerative forces on said weight element are substantially doubly integrated, travel of said weightv element thereby representing proportional travel of said missile, a tab extending from said gear and rotatable therewith, said tab extending to lock said weight element `against movement upon rotation of said tab through a predetermined angle, said tab permitting movement of said weight element to said nal position when said weight element travels at least some predetermined distance relative to the time required before said tab rotates through said predetermined angle.

References Cited in the tile of this patent UNITED STATES PATENTS 2,537,953 Andrews Jan. 16, 1951 2,789,508 Rove Apr. 23, 1957 2,863,393 Sheeley Dec. 9, 1958 

